The growth habit is horizontally spreading, though the plant may reach a height of up to 3 feet. The branching is stiff and dense, giving the plant a rather bristly look. Stems shoot off the branches at an angled herringbone pattern. The shiny leaves are small and roundish, with a fine texture that provides a nice contrast to larger-leafed plants. The fall color ranges from reddish-orange to burgundy. The light pink blooms of late spring yield later to equally shiny red berries (or “pomes”). These red berries stay on the branches for a long time and remain attractive into early winter. By late winter the withering berries continue to lure hungry wild birds. Rock cotoneaster is easy to grow; in fact, for some gardeners, it may be a bit too easy to grow, requiring considerable pruning to keep it from spreading. These shrubs are best planted in spring; they have a rather shallow root system that needs time to become established before the winter months. It is a fairly slow-growing shrub, taking several years to reach its maximum 3-foot height. In the meantime, though, the plant will be eagerly spreading out horizontally. The dense branching habit can make it difficult to clean away ground debris from around the plant. For some gardeners, the shrub’s ability to spread so easily is a drawback.
Light
Give rock cotoneaster full sun for optimal berry production and fall-foliage color.
Soil
This plant is not fussy about soil pH, although it generally performs best in soil with a roughly neutral soil pH. Its main soil requirement is good drainage. A loamy soil works best.
Water
Rock cotoneaster is a drought-tolerant shrub once established. But until it is established, water regularly so as to keep its soil evenly moist.
Temperature and Humidity
Rated for use in USDA zones 5 to 7, these shrubs will be deciduous in the northern end of the range, but evergreen in zone 7. These plants struggle in hot conditions, so don’t try to grow them south of zone 7. These plants do well in relatively low humidity; humid weather may cause fungal leaf spots, though this is rarely a life-threatening problem.
Fertilizer
Rock cotoneaster is not a heavy feeder. Add compost to the soil as needed.
Pruning Rock Cotoneaster
It is not necessary to prune cotoneaster plants for the health of the plant, but you may want to do so to contain their spread. And if you do prune them, don’t trim off the stem tips, as this will ruin the naturally graceful shape. If you feel that a particular branch spoils the overall shape of the plant, follow the branch all the way back to the center of the shrub and make your pruning cut there. Rock cotoneaster is one of those bushes that will strike down roots wherever one of its branches touches the ground. This enables it to spread fairly rapidly. If this is an undesirable trait for you, then you’ll need to keep up with your pruning to restrict the bush’s spread. If low-maintenance landscaping is a priority for you, you may wish to skip rock cotoneaster altogether and grow a plant that is more demur.
Propagating Rock Cotoneaster
The easiest way to propagate this plant is by stem cuttings. In July or August, cut away some of the plant’s healthy side shoots, cutting just below a leaf node. Remove the lower leaves and plant the cuttings into a gritting potting medium. Cover the pot with a clear plastic bag or dome, and place it in a bright location. When new shoots begin to appear, remove the cover and continue to grow indoors. By the following spring, the new specimen will have a good root system and will be ready to plant in the landscape.
Common Pests/ Diseases
There are no truly serious insect or disease issues with rock cotoneaster, but it can be susceptible to some of the same problems that afflict other members of the rose family. Fireblight, leaf spots, and canker may be problems. Branches showing signs of fireblight or canker should be removed and destroyed. Leaf spots may require treatment with a garden fungicide if the symptoms are severe. The most serious insect pest is the cotoneaster webworm, which can skeletonize the leaves. Webs will be visible on leaves and branches. These pests are difficult to control, and usually require the application of a chemical pesticide.
Landscape Uses
Two of the common names for C. horizontalis—rock cotoneaster and wall cotoneaster—give a strong hint of its uses in the landscape. These spreading shrubs are often used as sprawling rock garden plants, or to cascade over retaining walls or embankments. More broadly speaking, rock cotoneaster works well as a ground cover in any sunny spot where you need a plant to fill in a patch of bare ground. Birds, bees, and butterflies are all attracted by these bushes. Birds use cotoneaster berries as an emergency food source in winter. At the same time, these stiff, dense shrubs are deer-resistant.
Rock Cotoneaster vs. Other Cotoneaster Species
The cotoneasters are a diverse group of plants and are roughly divided into ground-cover types (such as Cotoneaster horizontalis) and taller, more upright types. Within the rock cotoneaster species, there are two varieties to consider. One is a naturally occurring variety (C. horizontalis var. perpusillus), which grows only 1 foot tall, making it an ideal ground cover plant. And there is a cultivar, ‘Variegatus’, which has two-toned leaves. But there are also many species besides C. horizontalis, including:
Cotoneaster dammeri is one of the shortest types, reaching just 8 to 12 inches tall (suitable for zones 5 to 8). C. divaricatus is one of the kinds that grow tall enough (up to 6 feet in height, with a spread of up to 8 feet) to be used in a hedge (suitable for zones 4 to 7). C. lucidus is another kind commonly grown in hedges. It grows to be 6 to 10 feet high and wide (grow it in zones 3 to 7). C. salicifolius is one of the taller types at 10 to 15 feet tall, with a spread of slightly less than that (suitable for zones 6 to 8).
